Planning your trip takes time and effort and one of the first things that I consider is weather. It is appropriate to decide on a destination however it is also smart to consult the weather. A friend once told me she and her girlfriends were planning a trip to Greece in December. I replied 'have you considered the weather?' and she said 'why'. Well it is rather wet and cold in December and if you are visiting the islands there would be very limited accommodation open. It is a travel fact the most hotels and pensions on the islands open from 1st April to 30th October, a few do stay open islands such as Santorini and Mykonos however you would have to check.
So questions you should ask yourself or Google are what is the best time of the year to travel. Do you want to go in Autumn or Spring for example. We went to Italy in June and the locals said it is a very good month to travel, not so hot although we did get temperatures in the mid 30's but it is dry then too.